A factor analysis kf 25 possible signs of minimal brain dysfunction defined factors representing school achievement (learning disabilities), hyperkinetic-impulse disorders, social immaturity, and minor neurological problems (neurological soft signs). All children were given scores on each of the four factors, and correlation coefficients have been calculated between these scores and over 600 antecedent and concomitant variables. Many socioeconomic, maternal, neonatal, and developmental variables have significant associations with the factor sckres. Children with symptoms in more than one area are more common than would be expected if there were no association among symptoms across the four areas, although most children who have problems in one area do not have problems in other areas. Cases will be grouped by symptom patterns and examined separately for associations with antecedent variables. Twin and sibling studies suggest moderate genetic influence on the achievement factor score, low genetic influence on the hyperkinetic and immaturitY scores, and still less influence on the neurological scores.